The present invention is directed to a novel laminated panel which has a rigid foam core. Laminated panels having rigid foam cores are known in the art. See, e.g., U.S. Pat. Nos. 3,900,651, 3,903,346, 3,940,517, 4,025,687, 4,028,158, 4,043,719, 4,118,533 (and its Reissue 30984), 4,212,917, 4,271,273, 4,284,683, 4,292,353, 4,292,361, 4,292,363, 4,292,369, 4,296,170, 4,311,801, 4,316,935, 4,335,218, 4,346,133, 4,351,873, 4,362,678, 4,386,166, 4,386,983, 4,411,949, 4,438,166, 4,459,334, 4,467,014, 4,481,307, 4,496,625, 4,544,679, 4,555,442, 4,572,865 and 4,572,919.
It is known in the art to utilize fibers in various forms in the production of such laminated panels. The forms of the fibers and the reasons for their use are varied.
U.S. Pat. No. 3,900,651 relates to the same problem which faced the present Applicant, i.e., the production of a sandwich element designed to withstand high stresses. This problem is overcome in the '651 patent by adhesively joining flocked fibers to the facing material.
U.S. Pat. No. 4,025,687 relates to the reinforcement of the foam core. The core is reinforced by a "binding material" which may be embedded anywhere within the foam core but is preferably no deeper than approximately one inch from the outer surface of the foam core. Suitable "binding materials" disclosed are metal wires, filaments or meshes; glass, textile or plastic fibers, strands, filaments, strips or extrusion in single, random, woven or meshed form. As disclosed, the woven or meshed material must be of a sufficiently coarse mesh or weave to allow the foam to penetrate. Chicken wire is described as being the preferred material. As described, the purpose of the "binding material" was to prevent cracking of the foam core.
U.S. Pat. Nos. 4,292,361 and 4,292,369 describe the laying of a matted or woven fiber near the interface between the foam core and the facing material in order to enhance the fire resistance properties of the laminate.
U.S. Pat. No. 4,292,363 describes a laminated panel where a mesh of continuous glass fiber strands is embedded in multiple layers substantially throughout the thickness of the foam core. The laminate is described as a non-load bearing structure having enhanced fire resistance properties.
U.S. Pat. No. 4,438,166 describes adhering a facing material to a thin, substantially incompressible, yet expansible mat of long, layered glass fibers in order to reinforce the foam core.
U.S. Pat. No. 4,459,334 describes the use of a non-woven, relatively open glass fiber mat in order to increase the surface strength of the facing material, to increase the flex strength and dimensional stability of the laminate, and to offset any facing material delamination.
U.S. Pat. No. 4,572,865 describes the use of glass fiber for foam reinforcement purposes.
Finally, U.S. Pat. Nos. 4,028,158 (and its Reissue 30984), 4,284,683, 4,346,133 and 4,386,983 describe the use of a mat of long straight glass fibers arranged in layers and distributed evenly throughout the foam core in order to reinforce the core.
The covering of the back of the facings with non-woven fiber webs or the use of reinforcing webs such as glass fiber fabric is intended to increase the mechanical strength especially immediately underneath the facings and to improve the bond between the facings and the foam core as well as to obtain a profile of decreasing density from the facing layers to the center of the foam.
Facing materials are generally used which are impermeable or almost impermeable to gas. Gas bubbles of varying size accumulate underneath the upper facing as the foam expands. These gas bubbles subsequently make their mark on the visible surface of the product if the facings are thin sheets. The irregular bulges formed on the surface not only mar the appearance of the product but also increase the risk of damage to the facings at these points. It has been found that even the use of the conventional meshwork webs such as glass fiber fabrics and non-woven fiber fleeces cannot prevent the formation of gas bubbles. It was found that, depending on the particular nature of these webs, they sometimes showed patches that were completely free from foam, evidently because they had been completely penetrated by gas bubbles. In other cases, the reaction mixture had crept along inside a web, evidently due to capillary action, and formed a film of foam underneath which the gas bubbles accumulated. Although the film of foam together with the reinforcing web had to some extent stabilized the facing, these hollow patches were still more likely to be damaged by sudden impacts.
The problem facing the present Applicant was to eliminate the bubbling effect noted above while at the same time reinforcing the facing material so that the final laminate could withstand high stresses.